Agent Orange is one of several herbicide preparations used by the U.S. Defense Department to destroy forests and enemy crops in Vietnam in the 1960s. Agent Orange contains a 50:50 mixture of two herbicides: 2,4-D (2,4-dichlorophenoxyacetic acid) and 2,4,5-T (2,4,5-trichlorophenoxyacetic acid). A contaminant of 2,4,5-T is TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin), which is highly toxic to animals.

During the Vietnam conflict, North Vietnamese guerrillas found cover in the lush jungles of South Vietnam. To deprive their opponents of cover and food crops, the U.S. military sprayed Agent Orange and other herbicides on about 6,600 sq mi (1,709,000 ha), an area equivalent to one tenth of the land mass of South Vietnam. This military strategy is regarded as having saved the lives of many U.S. combat soldiers. The bulk of the herbicides were applied by "Operation Ranch Hand," a tactical program for spraying herbicides from airplanes by the...